Since risks of cross contaminations between different patients or between patients and care givers have been taken into consideration, it is now customary or even compulsory for the medical delivery device to be used once only for a specific patient, as certified by the development of “disposable” equipment sold as being sterile and discarded after use. Similarly, medicines are more and more frequently sold in vials containing a single dose, making it impossible to use it on several patients and limiting risks of dosage errors. However, despite the “disposable” indication signalled by medical delivery devices, there is nothing to prevent them from actually being reused on several patients. Thus for example, a needle for an intravenous injection can be connected to a syringe containing a dose of medicine and can therefore be used to deliver the said dose to several patients. Many solutions have been proposed firstly to the problem of reuse of these hypodermic needles and syringes, and secondly to accidental contamination by the injection, and invariably lead to single use of the syringe and/or the needle.
However, some medicines are in a form that needs to be prepared by dilution, for example a freeze-dried powder. Preparation of such a medicine consists of mixing the form to be diluted with a solvent in specific proportions and transferring the solution obtained into the medical delivery device. In general, the solvent is drawn up firstly with the syringe and is then injected into the receptacle containing the freeze-dried powder. After mixing, the mix is drawn up with the syringe again. The syringe is then connected to the medical delivery device so that the said mix can be administered. Consequently, the connection between the syringe and the various receptacles must be made and disassembled as often as necessary, in order to make the mix. The last connection made is the connection between the syringe and the medical delivery device.
U.S. Pat. No. 6,231,552 describes a connection assembly between a reservoir, in this case a syringe, and a medical delivery device, in this case a hypodermic needle. At the syringe, this connection assembly uses a standard male Luer cone surrounded by a coaxial cylinder at the cone with a thread on the internal face, and a notch is formed at the free end of the thread. The needle has a standard female Luer cone compatible with the male Luer cone on the syringe and a thread complementary to the thread on the syringe formed on the outer surface of the base of the hypodermic needle. Furthermore, a pin projects from the said external surface at the distal end of the needle thread. Thus, when the syringe is connected to the needle, after screwing to make the two threads mentioned above cooperate, the pin on the hypodermic needle clips irreversibly into the notch in the syringe provided for it. The resulting system prevents the reservoir and the medical delivery device from being disconnected, while enabling the standard male and female “lock” type Luer connectors to be reversibly connected (with a thread like that described above). The system becomes irreversible only when making the connection between Luer cones including either the projecting pin or the notch in which the pin will fit.
The disadvantage of this type of device is that the user must make a translation movement combined with a rotation movement (helical movement) to irreversibly connect such a system, and to make the connection while providing an additional force of the end of screwing to engage the said irreversible retaining means between the two elements, while the male and female Luer cones are already cooperating by contact so as to make the connection leak tight.